Renato Padovani, University Hospital, Udine, Italy

Transcription

1 DATAMED II Training Course Sofia, May 19-20, 2011 Patient dose assessment in fluoroscopy and interventional procedures Renato Padovani, University Hospital, Udine, Italy

2 Content Fluoroscopy guided diagnostic and therapeutic (interventional) procedures of interest in DATAMED II Technical and dose quantity of interest Effective dose: conversion coefficients Recommendations and pitfalls

3 Fluoroscopy procedures from 225 specific types of examinations or procedures (RP154)

4 Interventio nal procedures (RP154)... + every day new coming procedures

5 Procedures in the TOP20 list +... other procedures in the case you have frequency or dose information (in the 70 or 225 list)

6

7 5-60 min of fluoroscopy Several hundred of images

8 Technical and dose quantities Fluoroscopy time and no. of acquired images Not well correlated with patient dose Good indicators of the complexity of the procedure, the skill of the operator and procedure protocol KAP (DAP) Useful quantity for the assessment of effective dose Good indicator of the complexity of the procedure, operator skill, procedure protocol and equipment performance KAPfluoro and KAPimages can provide additional information the technique used Cumulative incident air-kerma (Ki) at the IRP Useful quantity to monitor skin dose

9 Sample size: Diagnostic procedures: patient/installation Therapeutic procedure: patient/installation Sample of hospitals Recommendations Quantities: To collect: Fluoro time, no.images, KAP Data analysis: To assess for each installation: Median values are good indicators of typical procedure to compare with RLs or literature values Mean values are necessary for dose assessment Max/min is indicator of procedure variability (variability in pathologies, skills of operators, etc.) To compare practice between installations: Compare median values (Assess national RLs)

10 To calculate effective dose Computational tools (e.g. PCXMC MonteCarlo, NRPB SR222, GSF,...): Require knowledge of irradiation geometry and radiographic parameters (kv, HVL, dose, field size, beam orientation and patient skin entrance point) Good exercise (data collected manually or from DICOM objects Dosimetry Report) To use averaged conversion factors (procedure and patient body area dependent) - recommended

11 Example: conversion coefficients for cardiac procedures E= c * KAP REF PROCEDURE N <KAP> <E> <E/KAP> (Gycm2 ) (msv) Betsou et al., BJR, 71 (1998) CA Broadhead et al, BJR,70(1997) CA Lobotessi et al, RPD,94(2001) CA Leung et al, BJR 69 (1996) CA Ospedale di Udine CA Betsou et al., BJR, 71 (1998) PTCA Broadhead et al, BJR,70(1997) PTCA Ospedale di Udine PTCA Broadhead et al, BJR,70(1997) RF Ablation Ospedale di Udine (2006) RF Ablation Ospedale di Udine (2006) PM/defibrillator

12 To calculate effective dose: recommended conversion coefficients (RP154) PTCA: 0.2 msv/gycm2

13 To play attention... Frequency evaluation Ba meal & barium enema & IVU: the procedure can produce more procedures (abdomen + Ba examinations or IVU) but dose is measured for the whole procedure A cardiac therapeutic procedure can be registered as 1 CA + 1 PTCA. Is dose measured for the whole procedure? Reimbursement system can affect frequency and dose evaluations

14 To play attention... KAP values: Is a common QC practice in the country to check the calibration of KAP meters? For undecouch examinations is the table attenuation taken into account. Typical attenuation factors are 10-20% Are operators aware of the different dose unit provided by machines (Gycm2, mgym2, cgycm2, ugym2, etc ) and possible registration errors? Is PACS/RIS dose value accuracy checked?

15 Equipment without KAP meter... Median Fluoroscopy time and no. of acquired images allow to compare the practice with published or available data from other installations and assign appropriate KAP value to the installation Or, leave to the DATA MED group to assign the mean dose from the whole database

16 Good work!!!!!!!!!!!!!!!!